1. Field of the invention
This invention relates to the production and use of new porphyrin derivatives, to metal complexes of porphyrin derivatives, and to compositions containing the porphyrin derivatives and the metal complexes. More specifically, some of the porphyrin derivatives are compounds for which the name benzochlorins is suggested because they have a chlorin structure with an exocyclic benzene ring fused thereto, metal complexes of the benzochlorins, verdins, metal complexes of verdins, derivatives which form when certain purpurins stand in sunlight in contact with air, and metal complexes of the derivatives which form when the purpurins stand in sunlight in contact with air. All of these compounds are useful in the detection and treatment of tumors; after they have been administered systemically, e.g., intravenously, they localize preferentially in a tumor. After they have been administered, and have localized in a tumor, their presence can be detected by illumination with ultra violet light, which causes them to fluoresce. The porphyrin derivatives of the invention can also be used to treat tumors; after they have been administered and have localized, irradiation with light of a wave length at which they show an absorbance peak causes a reaction which has been found to involve the formation of singlet oxygen, and which damages or destroys the tumor where they have localized. The compositions containing the porphyrin derivatives and metal complexes thereof arc solutions in an organic liquid that is physiologically acceptable for intravenous administration, emulsions thereof in saline solutions, or cyclodextrins in whose molecules the molecules of the porphyrin derivatives and metal complexes are encapsulated.
2. The Prior Art
Certain porphyrins and families of purpurins and chlorins and metal complexes thereof and the use of the purpurins, chlorins, metal complexes and porphyrins in the manner described above for the detection and treatment of tumors are all known. For example, PCT/U.S. Pat. No. 86/02824 discloses certain purpurins, chlorins, and metal complexes thereof, and their use for the detection and treatment of tumors. In addition, European patent application EP142,732 is said (C.A. 103:123271S) to disclose certain chlorins of a different family and that they accumulate preferentially in the cancer cells of hamsters infected with pancreatic cancer.
Further, a chemical mixture derived from hematoporphyrin, called hematoporphyrin derivative, and often abbreviated "HpD", can be administered intravenously and used in the manner described above for the detection and treatment of tumors. Hematoporphyrin can be produced from protoporphyrin IX, a porphyrin that can be separated from blood. HpD is a mixture of many different porphyrins and related compounds, the exact composition not being fully known (see, for example, Porphyrin Photosensitization, edited by David Kassel and Thomas J. Dougherty, Plenum Press, New York and London, 1983, pp.3-13). As a consequence, the chlorins and purpurins of PCT/U.S. Pat. No. 86/02824 are preferred over HpD for this use because they are single, known compounds. In addition, the chlorins and purpurins have absorbance peaks at longer wavelengths and show greater absorbances, by comparison with HpD; the longer wavelength peaks are advantageous because light of the longer wavelengths is capable of greater penetration of tissue, while the greater absorbances are desirable because less light energy is required to cause a given degree of reaction.
The production of the nickel complex of an octa-ethyl benzochlorin has been disclosed (Arnold et al., J. C. S. PERKIN I, pages 1660-1670, 1979). The complex is produced by reaction in dry N,N-dimethylformamide between phosphorus oxychloride and nickel meso-vinyl octaethylporphyrin. The major product reported was nickel 5-(.beta.-Formylvinyl) octaethylporphyrin (80 percent yield); in addition, the authors reported a 5 percent yield of the nickel benzochlorin and a 15 percent yield of a demetallated product (which was not a benzochlorin). The nickel octaethylbenzochlorin has been found to be substantially inert insofar as the ability to cause a cytotoxic response is concerned.
The production of a verdin isomer mixture by refluxing a mesorhodin isomer mixture in acetic acid has been reported (The Porphyrins, Volume II, pages 137 and 138, edited by David Dolphin, Academic Press, New York, San Francisco and London, 1978). Woodward et al. J.A.C.S., 1960, 82, p. 3800 and Morgan, J. Org. Chem., 1986, 51, 1347 disclose that the porphyrin derivatives form when purpurins stand in sunlight in the presence of air.
The benzochlorins, the verdins, the derivatives which form when purpurins stand in sunlight in contact with air and metal complexes of the instant invention have the same advantages as the purpurins, chlorins and metal complexes, and, in some cases, the significant additional advantage that substantially smaller doses are required to cause a given cytotoxic response.